The characteristics of the superconducting and magnetic phases in the polycrystalline samples of ruthenocuprates of nominal compositions RuSr2GdCu2O8, Ru0.98Sr2GdCu2O8 and Ru0.5Sr2GdCu2.5O8-d - Condensed Matter > Superconductivit

Abstract: The temperature dependencies of the resistivity for the superconductingruthenocuprates of nominal compositions RuSr2GdCu2O8, Ru0.98Sr2GdCu2O8 andRu0.5Sr2GdCu2.5O8-d were examined for the magnetic field dependentcharacteristics of the superconducting transitions. The effect of theinsignificant diminishing of the Ru-Cu ratio in parent RuSr2GdCu2O8 wasconfirmed as relevant for the stabilisation of the superconducting phase. Noteddifferences in the compared characteristics are interpreted for possibleinhomogeneous nucleation of the superconducting phase in the parentruthenocuprate. The phase anisotropy in RuSr2GdCu2O8 and Ru0.98Sr2GdCu2O8 , inpresence of the compounds Ru magnetism, appears to be a cause of a significantsoftening of the Hc2T phase line. An anomalous lowering of themagneto-resistivity was observed in the approx. 10 K range above the onset ofthe superconducting transition, which may suggest the presence of enhancedsuperconducting fluctuations in the samples. The positive magnetic field shiftof the temperatures, which limit the magneto-resistivity and the specific heatsignatures of the magnetic ordered state of the Ru sub-lattice, suggestsprobing the influence of the ferromagnetic Ru interactions in an effectivemetallic-like conduction channel present in the samples. Superconductingcharacteristics of the Ru0.5Sr2GdCu2.5O8-d reveal a significant contribution ofthe Gd paramagnetic signal at low temperatures, interpreted for the presence ofa significant anisotropy of the superconducting phase. It is concluded that theRu-Cu substituted phases of ruthenocuprates may present an opportunity toinvestigate the effectively anisotropic superconducting phase despite itscomparatively high Tc in the compounds related to the 123-type cupratesuperconductor.